Study On A New Polypropylene Foam Filter For Lead-acid Battery

A few gases are produced while the lead-acid battery is working.The gases are usually exhausted from the inner part of the lead-acid battery by installing a air filter.At present,the type of air filter which is widely used is PTFE filter.This air filter is high cost,poor ventilation and poor mechanical strength.It can be inhaled into the battery easily,when the battery has a internal negative pressure.It has great value and broad prospects to develop a new type of air filter.It is suitable to develop the air filter which is made of polypropylene（PP）for its low price and high strength.The goal of this investigation was to develop a eligible PP filter.Firstly,the age resistant and mechanical properties of PP were improved by addition of antioxidants.Secondly,the melt strength of PP was improved by addition of cross-linking agents,so that the gases could be well wrapped in it.Thirdly,the decomposition mechanism of azodicarbonamide（AC） was researched deeply.In order to reduce the decomposition temperature of AC,some modifiers were added to it.Finally,the optimum forming conditions of PP filter were selected by orthogonal experiment.Main contributions of this study are as follows:In this paper,the age resistant and mechanical properties of PP was improved by addition of three antioxidants.[Pentaerythritol tetrakys 3-（3,5-ditert-butyl-4-hydroxyphenyl）propionate]（I1010）was used as primary antioxidant,tris（2,4-ditert-butylphenyl）phosphite（I168）and dilauryl thiodipropionate（DLTP）were used as auxiliary antioxidan.The results showed that the heat resistance ability of PP has been effectively improved,the processing performance has been improved significantly and the yellow index（YI）has decreased by addition of the antioxidants.Compared with I1010/ DLTP,I1010/I168 system has a good anti-thermal oxygen degradation effect.PP was at the best processing performance and the lowest yellowness index（YI）while with the optimal addition amount of I1010/I168 in PP is 0.2 %.In this paper,the crosslinking behavior of PP was studied,the processing performance of PP was increased with the increment of DCP content.When the amount of DCP exceeded 2% or the amount of abietin was used more than 3%,the performance of polypropylene began to fall.The decomposition mechanism of AC was studied by thermal analysis and FTIR analysis.The results showed the decomposition mechanism of AC contains three decomposition stages.The main products of the first phase are N₂ and CO₂,the solid products are diurea and urea.When the amount of ZnO was more than 1.25%,the decomposition temperature of AC was reduced from 209°C to 179℃～182℃,when the amount of Zn St was 12.5%,the decomposition temperature of AC was reduced to 166℃.The decomposition temperature of the blowing agent was not much different from the melting temperature of PP,it was suitable for foam molding.In the L₉（3⁴）orthogonal experiments,it showed that the best molding temperature was 195℃,the best molding time was 1.5min,the best molding pressure was 1MPa.